This invention is generally directed to toner, carriers and developer compositions, and more specifically, the present invention relates to developer compositions containing carriers. In embodiments of the present invention, the carrier particles can be comprised of a core, a polymer, or mixture of polymer coatings thereover, and which coating or coatings have incorporated therein an intrinsically conductive polymer (ICP) additive of, for example, LIGO-PANI® available from GeoTech Chemical Company, or EEONOMER® available from Eeonyx Corporation. The LIGO-PANI® is believed to be an ICP comprised of polyaniline segments or chains attached and grafted to Lignin; and the EEONOMER® is believed to be comprised of an ICP of a polypyrrole or a polyaniline polymer deposited on a carbon black matrix, and which depositing is accomplished, for example, by an in situ polymerization. In embodiments, the conductivity of the ICP is, for example, from about 10 to about 50, and more specifically, from about 10 to about 40 Siemens/cm measured, for example, utilizing a pressed pellet per ASTM F84 and D257. The particle size median diameter of the carrier additive coating, such as the ICP, is, for example, equal to or less than about 100 nanometers, such as from about 25 to about 75 nanometers, or more specifically, a particle size distribution wherein 99 percent of the particles are of a diameter of below about 100 nanometers, that is for example about 1 percent of the particles are as large as 300 nanometers. The carriers of the present invention may be mixed with a toner of resin, colorant, and optional toner additives to provide developers that can be selected for the development of images in electrostatographic, especially xerographic, imaging systems, printing processes and digital systems.
Advantages of the carriers of the present invention in embodiments include, for example, the selection of certain inherently conductive polymers as carrier coating additives wherein the electrical conductivity thereof can be tailored to encompass the range from insulators to semiconductors to metals, and wherein the conductivity can increase linearly with the amount of conductive polymer present; substantial carrier thermal stability, for example, up to 300° C.; tunability of the carrier conductivity without substantially adversely affecting the carrier and developer triboelectric charge; eliminating or minimizing the known black mottle disadvantages related to developer conductivity differences between various carriers; utilization of low amounts of the polymeric ICP additive to achieve the same or similar conductivity as compared to higher amounts of, for example, a conductive carbon black; wear resistant carrier coatings thereby avoiding or minimizing color contamination in machine housings; compatibility with polymer coatings, such as polymethylmethacrylates (PMMA); excellent and stable high triboelectrical carrier and developer characteristics; the generation of economical carriers and developers; utilization of the carriers and developers in hybrid scavengeless systems wherein the conductivity increases without a corresponding triboelectric charge decrease; and the like. Compatibility of the conductive polymer with the host polymer coating is believed to be excellent as compared to, for example, blends of inorganic fillers or conductive additives, and this advantage can be achieved with the present invention in embodiments, it is believed, because of the partial miscibility of the conductive polymeric component and the nonconductive polymer hosts, which serve to eliminate or minimize the sharp interface between the host polymer and the inorganic filler, which is typically the point of weakest mechanical integrity in the composite, and is the point where the material fractures on the surface of a carrier in a xerographic environment.
The carriers and developers of the present invention can be selected for a number of different known imaging and printing processes including, for example, multicopy/fax devices, electrophotographic imaging processes, especially xerographic imaging, and printing processes wherein negatively charged or positively charged images are rendered visible with toner compositions of an appropriate charge polarity. Moreover, the carriers and developers of the present invention in embodiments can be selected for color xerographic imaging applications where several color printings can be achieved in a single pass.